1. Field of the Invention
The present invention relates to ink jet recording apparatuses, and more particularly, to an ink jet recording apparatus that can drive a piezoelectric element by applying a pulse voltage of a plurality of waveforms.
2. Description of the Related Art
Piezoelectric elements are conventionally used in the recording head of an ink jet printer. In such a recording head, the strain of the piezoelectric element driven by the applied voltage causes pressure to be applied to the ink within a predetermined closed cavity (ink channel). The ink is sprayed out towards a recording sheet from a nozzle provided in the ink channel in the form of ink droplets.
Ink droplets of a plurality of different size can be ejected by altering the level of the pulse amplitude of the rectangular pulse voltage applied to the piezoelectric element. Each ink droplet of various different size corresponds to a print dot diameter on the recording sheet. The half tone can be represented by controlling the magnitude of the pulse amplitude.
In such a printout by a rectangular pulse voltage, particularly in a printout of ink droplets of a greater diameter, various undesirable phenomena such as satellite (an ink droplet corresponding to a certain print dot diameter is sprayed out accompanying generation of a small ink droplet), dot split (the tip of the ink droplet sprayed out is split into two), curve (the direction of the ink droplet to be sprayed out is deviated) and the like are encountered. These phenomena of satellite, dot split, and curve become the cause of satellite dots, dot split noise, and ink hit position offset to significantly degrade the picture quality of the reproduced image.
Furthermore, in printout by means of a rectangular pulse voltage, particularly when the printout frequency which is the frequency of the pulse voltage to be applied is increased, similar undesirable phenomena such as satellite, dot split, and curve occurs. Thus, the picture quality of the image is significantly degraded by these phenomena.
Generation of a wave in the ink within the ink channel after an ink droplet is sprayed out towards a recording sheet is considered to be one cause of these phenomena of satellite, dot split, and curve. Although this wave is attenuated over time, application of a pulse voltage corresponding to the next ink droplet with the wave still occurring in the ink within the ink channel will cause the above-described satellite, dot split and curve phenomena.